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International Rivers is not the biggest fan of hydroelectric dams, but the U.S. based non-profit recently used Earth technology to get river lovers and the curious to finally see things their way.

Their "State of the World's Rivers", which launched on Tuesday, blames the big dam builders for messing with nature. The online interactive illustrates just how dams have impacted rivers from the Mississippi to the Amazon, the Danube to the Yangtze. According to the study, the biggest impact has been on water quality. The Mississippi River basin was considered one of the worst. America's longest river has 703 dams. No river on earth has more dams than the Mississippi, not all of them power stations. The U.S. garners about 9% of its electric power from water-based systems, compared to about 80% for Brazil, the world's leader in hydroelectric power generation.

The Three Gorges Dam along China's Yangtze River is the world's largest. It came with a heavy environmental price. International Rivers, an NGO, wants the World Bank to reconsider funding of hydroelectric dams. (Photo credit: Wikipedia)

International Rivers protested the massive Three Gorges Dam in China. Built along the Yangtze River, it has caused massive environmental damage and cost over-runs. The dam, known as the world's largest in terms of generation capacity, rerouted Yangtze tributaries that caused the trash of river communities to congregate downstream in what the The New York Timescalled "archipelagos of garbage". Landslides have also been a problem, especially in the years immediately following Three Gorges launch in 2006. Critics like International Rivers have also complained that China was unable to resettle the 1.4 million people displaced by the dam.

In Brazil, along the Amazon tributaries of Para state, private construction firms are currently building the 11,300 megawatt Belo Monte dam, which was supposed to be fully operational by 2015. The multi-billion dollar dam is expected to cost around $16 billion, more than the original plan of $11 billion. It has met with protest since the Brazilian environmental protection agency, Ibama, signed off on its construction some four years ago.

River basins fragmented by dams and polluted by mercury accumulation are public health emergencies that impoverish people’s quality of life. International Rivers, an environmental lobby, is targeting big hydropower funders like the World Bank in hopes to persuade them against dam project financing.

However, in countries like Brazil and China, long-term financing from multilateral lenders is not needed. Belo Monte, for instance, is almost entirely government financed by BNDES, a government run development bank that has more disbursements than the World Bank.

The World Bank approved financing for 12 hydroelectric projects throughout the emerging markets this year. The most recent was a $46 million commitment to Kabeli Energy Limited to build a $108 million hydroelectric power station in Nepal.

Dams have few fans outside of government and big industry.

Environmental groups have been targeted them for years. International Rivers is just one of them. Amazon Watch and the Hydropower Reform Coalition (HRC) is another. It's not that they're entirely against dams -- though most come down against the monster projects like Belo and Three Gorges. They just think the state EPAs have to do a better job assessing future risks to water supply. And that dams should be small.

The larger the dam, the bigger the mess, scientists agree.

Organic materials from within and outside a river now partially blocked by heavy power generating turbines tend to get built up behind dams and start to consume a large amount of oxygen as they decompose. Without the dam, they would have washed up down river, broken apart, hit the shore or hit the open sea. In some cases, this build-up can trigger algae blooms where none ever existed, creating river “dead zones” incapable of supporting life.

Water temperatures in dam reservoirs can differ greatly between the surface and depths, further complicating survival for marine life. And when dam operators release oxygen-deprived water with unnatural temperatures into the river below, they harm downstream environments as well, according to the HRC.

Thanks to the Mississippi River, the U.S. is home to more dams than any other country with 887 American dams making up part of the International Rivers study.

According to the U.S. EPA, hydropower plants alter large swaths of land where dams are constructed, requiring the flooding of land that may have once served as wildlife habitat, farmland, or residential areas. Hydroelectric dams can cause erosion along the riverbed upstream and downstream, which can further disturb wildlife ecosystems and fish populations.

They can affect various fish populations in different ways. Certain salmon populations in the Northwest depend on rivers for their life cycles. These populations have been dramatically reduced by the network of large dams in the Columbia River Basin. When young salmon travel downstream toward the ocean, they may be killed by turbine blades at hydropower plants. When adult salmon attempt to swim upstream to reproduce, they may not be able to get past the dams. For this reason, some hydroelectric dams now have special side channels or structures to help the fish continue upstream.